Pre-Season 7: Bounty Hunter vs Battle Trance for ADCs

Bounty Hunter: Grants 1.5% increased damage for each UNIQUE enemy champion you kill. Battle Trance: Grants up to 5% increased damage over 5 seconds when in combat with enemy champions.

Even if you kill the enemy adc and supp, you only get 3% more permanent damage and battle trance seems to give more early game pressure if you go for extended trades... but bounty hunter has more potential for more damage and can seem pretty snowbally?

Bounty Hunter=late game and Battle Trance=early game. Double Edge sword seems really good if you can avoid dmg... Thoughts on which is better for what adcs?